The instant invention relates to a friction winding shaft, in particular for roll cutting and winding machines wherein tube-shaped winding cores are fitted onto the shaft and driven to wind up strip-shaped bands.
A preferred but not exclusive field of application for this friction winding shaft is the winding of strip-shaped bands or film, such as adhesive strips divided from a production web into narrow strips and wound upon tube-shaped winding cores. In this process several winding cores are slipped next to each other on a shaft and are rotated in a winding direction. The transmission of torque to the winding cores takes place individually through frictional engagement, so that if a blockage occurs only one single winding core stops. At the same time a uniform winding pull is applied by each tube. Thanks to the predictable winding pull, the quality and precision of band winding is improved.
Roll cutting and winding machines using two friction shafts spaced from each other for winding the strip-shaped bands where adjacent bands are wound on different friction winding shafts and every other band is wound on the same friction winding shaft are known (DE 28 56 066 A1). A plurality of adjacent winding rings is slipped on a drive shaft to rotate the winding cores. The rings are provided with longitudinal slits in their outer surface area into which the leaf springs are inserted. The leaf springs extend inclined towards the radial in driving direction and their free ends press with pre-stress against the inner surface area of the winding cores.
Another friction winding shaft comparable in its structural concept but modified in its design is known (DE 42 44 218 C1). Winding core clamping elements in the form of spring-loaded rotating parts are used as holding devices with contact edges projecting from an outer holding ring surface area. The roof-shaped contact edges are somewhat inclined relate to the radial in driving direction and press with the force of a biased spring against the inner surface area of the winding core.
The procedure at the beginning of a winding process, as well as at its completion, is the same for both arrangements described above. The winding cores are first slipped on the rings, and the winding cores are turned on the shaft in the direction of the existing inclination of the leaf springs or with simultaneous pivoting of the clamping elements relative to the radial. The bands to be wound up are then attached to the winding cores and the friction winding shaft is started. When the winding cores are full with wound-up bands, the bands are severed so that the pull tensions on the band ends. To remove the winding cores from the friction winding shaft they are rotated relative to the stopped rings in the previous driving direction. This is possible because this rotation takes place in the direction of the inclination of the core clamping elements (spring-loaded clamping elements or leaf springs). Through rotation in this direction and lateral displacement, the full winding cores can be removed and new winding cores can be installed.
The structure of the friction winding shaft and the arrangement of the installed winding core clamping elements is determined by the operating method of the roll cutting and winding machine, and in particular by the selected direction of shaft rotation.
For the sake of completeness, friction winding shafts elsewhere having a different structure such as shown, for example, in U.S. Pat. No. 4,693,431, are known where ball elements moving in channels inclined towards the outer surface are used as clamping elements.
For these reasons, the direction of rotation in production operation must be known when ordering and installing the friction winding shaft. Care must be taken to ensure uniform installation of the rings and to ensure their proper direction, so that a torsionally effective coupling of the installed winding cores can be ensured. A friction-winding roller provided in this manner can not be used on a roller-cutting and winding machine rotating in the opposite direction because the winding cores would slip. In order to be used with an opposite direction of rotation, the rings would have to be removed from the drive shaft, turned around and reinstalled, causing considerable effort and expenditure.
Accordingly, an object of the present invention is to develop the design of a friction winding roller that is flexible in its application while remaining easy to handle, in particular in the installation of the winding cores.
The objectives of the invention are accomplished according to the present invention by providing a friction winding shaft and winding cores having the characteristics described in claim 1. Winding rings carried on the friction drive shaft include recesses in which clamping elements are seated which engage and drive the tubular winding cores. The clamping elements are aligned on both sides of the recesses in such manner that the clamping elements of each ring, when in their pivoting stop clamping positions, have clamping tips defining a curve with a diameter that is less than, or at most equal to, an inside diameter dw of the winding core, while a diameter dt of a circular curve defined by the clamping element tips in a dead center position is greater than the inside winding core diameter dw. The design of a friction winding shaft according to the invention affords the special advantage that winding cores rotating in either selected direction of rotation may be installed without any problem. A torsionally effective coupling of winding core and the friction winding shaft is ensured in the direction of rotation under load, i.e. during the winding process. Thus, a single friction winding shaft design is required for either direction of rotation. A reduction of manufacturing cost, and in particular logistics costs, is achieved when ordering and shipping, in storage, and in use.
The clamping element no longer bears on a lateral support surface of a ring recess but, contrary to the state of the art, bears with it cylindrical base body on the bottom of the recess. According to a further development of the invention, if the clamping element tip forms a sharp angle xcex4 with a peripheral force Fu1 or Fu2 of the winding core opposite to the direction of rotation D1 or D2 of the drive shaft so that the clamping element is located near the stop position of its pivoting path, the tip is able to engage and interlock more with the inner surface of the winding core.
In a further advantageous development, each winding ring recess for a clamping element is axially symmetrical to an axis of symmetry constituted by a radial of the winding ring whereby the dead center position of each clamping element is aligned with the radial. This is advantageous because of easier installation of the tubular winding cores, and the reliability of the clamping connection under load is found to be equal with either direction of rotation of the friction winding shaft. In order to be able to ensure this symmetrical radial arrangement or dead-center position of each clamping element, a notch for the seating of a spring wire is provided in the clamping element to ensure that the spring loading is aligned orthogonally relative to the axis of symmetry formed by the radial.
Clamping elements with offset tips and a tip angle xcex1 of 50xc2x0 to 60xc2x0, preferably 54xc2x0, and with bilateral inclines of about 45xc2x0 (angle of inclination Y), ensure an optimal torsionally strong coupling or clamping connection as well as easy installation of the winding cores. To bring about optimal positive locking between the inside surface of the winding core and the offset clamping element tip, a recess opening xcex2 of approximately 30xc2x0 is proposed in connection with the tip angle xcex1.